There have been developed various gas masks which are used for refuge in a fire. Many prior gas masks comprise either filter layers which have active carbon interposed between the adjacent filter layers or a catalyst of noble metal such as expensive platinum. Such gas masks are disadvantageous since they cannot be reused and therefore have to be discarded after a length of time.
Futhermore, although the gas mask of filter layers with or without active carbon interposed therebetween can remove particles of white and black smoke from the air, they cannot fully absorb poisonous gases such as carbon monoxide, which causes the user to inhale them. Although the catalyst of noble metal such as platinum can effectively convert carbon monoxide into harmless carbon oxide, it is disadavantageously expensive and tends to quickly deteriorate in function when even a little organic matter in the form of particles of white and black smoke contacts the surface of the catalyst. Also, the prior gas masks have to be discarded after use or storage during a predetermined period, which is expensive. The users do not have a feeling of confidence of whether they can be used in a safe manner or not. Particularly, the gas mask having the catalyst of noble metal provided serves no function in case it is stored under poor conditions or in case the catalyst of noble metal is damaged by smoke.